Loud speaker



Feb. 14, 1961 G. J. SIELER LOUD SPEAKER Filed Aug. 23, 1956 A 33 UIQ" 33 /50 GEORGE JEROME slEfLER Y INVENTOR.

" FIG 5 United States Patent() LOUD SPEAKER George Jerome Sieler, 10460 San Pablo Ave.,

El Cerrito, Calif. v

Filed Aug. 23, 1956, Ser. No. 605,748

2 Claims. (Cl. 181-31) This invention relates to a loud speaker and, more particularly, to a loud speaker system combining direct radiation of high frequencies, and a cavity-tube port low pass iilter transmission from the driving unit to front radiation horn means. My invention is most useful in loud speaker cabinets for high fidelity reproduction of AM and FM radio reception and of phonographic recording `devices and any other electrically transmitted sound.

IIn accordance with the present invention the loud speaker system having the characteristics mentioned may be incorporated in a single cabinet of quite small size but which produces effective and desirable resonant frequency elevation and bass frequency amplification while at the same time avoiding phase cancellation all as compared to much larger cabinets constructed according to conventional bass reflex principles. In addition to accomplishing these objects, my invention provides a cabinet producing clear tones, wide ranges and high rang. Further, I am able to accomplish these objects within a cabinet simple to construct.

In the drawings:

Figure l isa front elevation view of a loud speaker according to my invention;

Figure 2 is a horizontal sectional view taken on line 2-2 of Figure El;

Figure 3 is a vertical sectional view Ataken on line 3--3 of Figure l;

-Figure 4 is a fragmentary perspective view of an end of the cabinet with the top wall removed; and

Figure 5 shows in cross-section a speaker system as in Figure l modified to omit a tube-port and horn.

Essentially, my loud speaker comprises a right rectangular cabinet having first a central opening in its front to exhaust treble notes from a driver unit in the cabinet and registered at said opening and, secondly, a pair of marginal openings to exhaust bass notes emanating from the rear of the driver unit. Ordinarily the marginal openings are directed forward and are positioned at opposite sides of the central opening. They may of course open laterally if desired.

The cabinet comprises the bottom wall 10, end walls 12, 14 and rear wall 16 and top wall 18. Front wall 20 has the medial opening 22 behind which is mounted the driver unit 24. Wall 20 with ends 12, 14 and bottom wall and top wall 18 also provides marginal openings 26, 28. These walls are secured together by fasteners and adhesive in customary cabinet-making techniques and in such a manner that they have desirable rigidity as required for loud speaker cabi-nets. Preferably the rear wall 16 is removable to permit servicing of the driver unit 24 within the cabinet when required.

The driver unit 24 is of conventional type and is mounted rearwardly of opening 22 within a cavity 34 formed by walls 10, 16, 118 and port walls 30, 32. As can be seen in Figure 2 cavity 34 is in the shape of a truncated prism with the driver unit located at the truncation and the cavity flaring rearward therefrom. Port walls extend vertically from bottom 10 to top y18* and for- -spaced relation back from front wall 20 and from the `driver unit 24. The walls forming cavity 34 being secured together acoustically tight, bass sounds from the driver unit backside must leave cavity 34 by passing around the forward edges of port walls 30, 32.

Horn walls 36, 38 extend vertically from bottom d0 to top 18 and rearward from the front wall 20 with vertical edges 39 terminating in spaced relation to back wall 16. Horn walls 36, 38 tend to converge with the rear portion of end walls 12, 14 respectively and define ilaring horns that discharge through openings 26, 28, also respectively. i

Each horn wall is spaced apart from and parallel to a port wall to lform a tube port for bass sounds between cavity 34 and one or the other horn 26 or 28 as the case may be. I designate the tube ports 40, 42 and each respectively extends between edges 33, 39 of walls 30-36 and Wall 3238.

A pair of low pass filter units is thus created by the acoustic capacitance of cavity 3-4 and the acoustic inertance of tube ports 40 and 42. The bass frequencies exhaust from the tube ports into the throats 42, 44 of horns 46, 48 from which they pass outward through the horn sections to be ultimately discharged through openings 26, 28.

A loud speaker according to this invention has been constructed as follows:

Angle of tube port relative axis Make and model of driver unit-Lansing D-130.

Such a speaker has an excellent bass response down to 50 cycles and usable bass output of 25 cycles. The driver unit identitied had a low register cut-off of 40 cycles and a high register cutolf of 10,000 cycles. In this cabinet the cavity-tube port low pass acoustic lter provided a cut-off frequency of about 70 cycles.

While I have identified a specific driving unit, this cabinet will work extremely well with Stephen, Jensen, and University, and other simple as well as coaxial units. This cabinet produces a fundamental bass output that is clean and at least two octaves broader than is obtainable in other baffle cavity cabinets.

By this construction and cabinetry, I provide a loud speaker system which combines direct radiation for the high frequencies and back loading of the driver unit for bass frequencies that are also front radiated. The interposition of the low pass filter unit between the back loaded driver unit 4and the horn throat tlattens the bass response in the manner of a bass reiiex cabinet. The choice of a relatively small capacity for cavity 34 raises the effective resonant frequency of the speaker. Tube ports 40, 42 are proportioned so that a definite damping action is effected upon the bass frequencies emanating from the back loaded cone of the driving unit. The tube ports only efficiently transmit the lower frequencies. Thus the action of horns 46, 48 is effective only below the resonant frequency of the system. While it is customary in bass reflex systems for the sound output of the speaker to fall olf at a steep rate below the resonant frequency, the cabinet design of this invention reverses the effect.

By comparison with equivalent output bass reex systems, this system permits the reduction of the volume of the cavity behind the driving unit thus allowing smaller cabinets to be used for high volume sound output. The

tube ports in conjunction with the cavity provide anti-v The speaker cabinet 48 of Figure 5 yincludes the driver unit 24 in cavity 54 from which tube port 50` passes bass frequencies to the throat 52 of horn 56. This modification in all respects performs as described. However, the bass frequency output is localized at a single side of the' output of the high frequenciesof the driving unit. Also note that tube port 50 parallels the rear wall 48 and joins horn 56 at the throat in a manner slightly different but functionally the same as with the cabinet of Figure 2.

The invention, in the forms here described, is presented in a manner thought to clearly show its successful lapplication. Other modifications and variations will readily occur to those skilled in the art here applicable. These forms and modifications coming fairly within the spirit and scope of the invention as set forth in the appended claims are considered part of this invention,

I claim:

l. A loud speaker, comprising: wall means forming a right rectangular cabinet, a main wall of said cabinet having a treble opening therein, a driving unit mounted in said opening for forward disch-arge, said cabinet also having bass openings therein located symmetrically relative said treble opening; port walls, each free at one edge, defining With the cabinet Walls a backloading acoustic cavity surrounding the backside of said driving unit, said acoustic cavity having a discharge opening adjacent the free edge of each port wall; a horn wall spaced parallel from each port wall, said horn Wall with said port wall and with the cabinet walls defining an elongated, straight tube port of uniform cross-section extending from the associated opening from said acoustic cavity; each said horn wall forming within said cabinet walls a bass horn having a throat at the end of the related tube port, said horn flaring outwardly to a bass opening from the cabinet;

the cross-sectional area of each tube port being less than the cross-sectional area of the related horn throat and discharging without constriction thereto.

2. A loud speaker, comprising: wall means forming a right rectangular cabinet; a pair of spaced apart, port walls, each port wall being joined at three edges to each of three cabinet walls, said port walls convergingly extending toward but terminating in spaced relation to a fourth wall, said port walls and the associated cabinet walls defining an Aacoustic cavity having two openings therefrom; said fourth wall having a treble opening between' said openings and a forward discharging driving unit mounted in said treble opening; a horn wall spaced parallel outward 0f each said port wall, and angularly disposed relative the end walls of said cabinet to lform a horn aring to a mouth at said fourth wall, each saidV horn Wall terminating in spaced relation to the Wall opposite said fourth wall and forming a horn throat; each said horn wall and its adjacent port wall forming a tube port .of uniform cross-sectionextending between the related acoustic cavity opening and the related horn throat, the cross-sectional area of each tube port being less than the cross-sectional area of its related horn throat.

References Cited in the tile of this patent UNITED STATES PATENTS 2,201,073 Bobb May 14, 1940 2,224,919 Olson Dec. 17, 1940 2,491,982 Kincart Dec. 20, 1949 2,550,336 Daniel Apr. 24, 1951 2,751,997 Gately June 26, 1956 2,765,864 Glenn Oct. 9, 1956 2,852,087 Ruschhaupt Sept. 16, 1958 2,866,513 White Dec. 30, 1958 A FOREIGN PATENTS 342,369 Great Britain Feb. 5, 1931 OTHER REFERENCES Audio Engineering (publication), page 25, November 1951, ISI-31.1.

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